FARM EXPERIENCE. ' 239 



our farm practice. I will imagine, for instance, that my crop 

 needs more potash. It is not necessary that I bring that pot- 

 ash from outside and put it on the land ; perhaps it will be 

 sufficient if I put something into the soil which will set the 

 potash already there into activity. These fertilizers are not 

 merely plant feeders, but they act as a means of unlocking 

 the fixed capital in the soil and setting it afloat. It may be, 

 in the case to which reference has been made, that the plaster 

 which was applied previously to the corn crop, had had the 

 effect to supply something which could not be supplied so well 

 on the other part of the land ; it may have been the sulphuric 

 acid, it may have been the lime, which plaster contains, or it 

 may have been this indirect action upon the soil itself. 



There is one other mode in which plaster and other similar 

 fertilizers may operate, which is a very interesting one. The 

 first hint we got of it was furnished by Mr. Lawes, the English 

 gentleman to whose experiments I have referred so often. 

 Many years ago he conducted some experiments for the pur- 

 pose of determining how much water entered into and es- 

 caped from the foliage of his plants. He prepared a number 

 of boxes, a foot or two deep, in which he placed soil of differ- 

 ent kinds, and sowed seeds of different kinds, as they would 

 be planted for agricultural purposes. He put covers upon the 

 boxes, with holes through them just large enough to admit 

 tlie stem of the plant, so that the foliage was exposed to the 

 air, and there was no other chance for evaporation of water 

 except through the foliage. He also had a hole through which 

 he could pour water, and he had a large balance constructed, 

 so that he could weigh the boxes every day during the months 

 of the growth of the plants. In connection with this experi- 

 ment he made some observations which enabled him to notice 

 the effect of various substances applied as fertilizers, and his 

 observations showed distinctly that in the presence of certain 

 substances the amount of water which went through the foli- 

 age was considerably less than in other cases with the same 

 kind of plants. Mr. Lawes, in stating his results, simply re- 

 ferred to that point, but paid no particular attention to it, and 

 the matter rested there for some ten years, when a German 



